Small molecule activation of innate immunity by Listeria monocytogenes

描述（由申请人提供）：细胞内病原体对宿主免疫和医疗干预构成独特的挑战，使这类病原体成为当代最大的人类健康负担之一。单核细胞增生李斯特菌是一种革兰氏阳性的细胞内病原体，激活两种不同的先天免疫途径，由感染细菌的细胞内位置（吞噬体或细胞质）划分。对细胞质细菌的独特反应导致了细胞质监测途径（CSP）的假设，该途径能够识别损害细胞质的病原微生物。该途径的激活导致IFN-2的产生，并已在多种细胞内病原体中得到证实，包括结核分枝杆菌、土拉菌、嗜肺乳杆菌、布鲁氏菌和克氏T.。活的、复制的细胞内微生物的检测依赖于结合微生物配体的宿主受体。目前，我们对单核增生乳杆菌的先天免疫检测中涉及的宿主受体和微生物配体以及许多其他这类病原体缺乏了解。单核增生乳杆菌活化CSP的详细分析表明，IFN-2的产生几乎完全依赖于多药转运体MdrM的存在。基于此，我们假设存在一种细菌衍生的小分子，能够激活CSP。现在，我们已经纯化并鉴定了一种来自单核增生乳杆菌的新型配体，可以直接激活CSP。不能产生这种配体的细菌将被用来表征其在细胞培养和小鼠感染模型中的发病机制中的作用。此外，使用不同的宿主菌株将允许表征由该配体在感染期间激活的先天免疫途径。最后，我们将使用固定化配体来鉴定相互作用的宿主蛋白，目的是确定宿主受体。细胞培养模型将用于验证鉴定的配体相互作用蛋白。

DESCRIPTION (provided by applicant): Intracellular pathogens pose a unique challenge to host immunity and medical intervention, making this class of pathogens one of the largest contemporary human health burdens. Listeria monocytogenes, a gram- positive, intracellular pathogen, activates two distinct innate immune pathways, delineated by the intracellular location (phagasomal or cytosolic) of infecting bacteria. A unique response to cytosolic bacteria has led to the hypothesis of a cytosolic surveillance pathway (CSP) capable of identifying pathogenic microbes that compromise the cytosol. Activation of this pathway leads to IFN-2 production and has been demonstrated with multiple intracellular pathogens, including M. tuberculosis, F. tularensis, L. pneumophila, Brucella, and T. cruzi. Detection of live, replicating intracellular microbes is dependent on host receptors that bind microbial ligands. Currently, we lack an understanding of the host-receptors and microbial-ligands involved in innate immune detection of L. monocytogenes, as well as many other pathogens of this class. Detailed analysis of CSP activation by L. monocytogenes showed that IFN-2 production is almost entirely dependent on the presence the multi-drug transporter MdrM. Based on this we hypothesized the presence of a bacterial derived small molecule able to activate the CSP. Now, we have purified and identified a novel ligand derived from L. monocytogenes that can directly activate the CSP. Bacteria that are unable to generate this ligand will be used to characterize its role in pathogenesis in both cell culture and murine models of infection. Furthermore, use of various host strains will allow for the characterization of the innate immune pathways activated by this ligand during infection. Finally, we will use immobilized ligand to identify interacting host proteins with the aim of determining the host receptor. Cell culture models will be used to validate identified ligand interacting proteins. PUBLIC HEALTH RELEVANCE: Given the important role of innate immunity in human disease and the potent response elicited by the cytokines generated from innate immune activation, a detailed understanding of the mechanism by which L. monocytogenes activates the immune system may give rise to many promising therapeutics. Immuno- modulating molecules from L. monocytogenes and the host proteins that recognize these molecules will provide targets that can be manipulated to treat various forms of human disease, with the most obvious applications toward new adjuvants, vaccines to treat microbial infection and malignancies, and novel interferon inducing therapies for cancer and viral treatment.